Dark spots on the left eye bag may be caused by nevus, pigmentation spots, trauma and other reasons. 1. Pigmented nevus: dark spots under the left eye bag may be pigmented nevus, pigmented nevus is usually dark brown or dark black, it is a benign neoplasm composed of nevus cells with localized aggregation of abnormally developed melanocytes, which is usually manifested as a round black circle with a smooth surface and clear boundaries. 2. Pigmentation spots: excessive sun exposure and irregular work and rest in daily life may lead to endocrine imbalance, which may cause pigmentation spots, resulting in the appearance of black spots under the left eye bag. 3. Trauma: dark spots under the left eye may be caused by trauma to the eye resulting in localized bruising, if not treated in time, bruising for a long time to accumulate, may lead to dark spots under the left eye. If the patient has a black spot under the left eye, it is recommended to consult a doctor in time and follow the doctor’s instructions for standardized treatment.